1. Field of Use
This invention relates to dynamic memory systems and more particularly to improving the reliability of such systems.
2. Prior Art
Recently, manufacturers of dynamic random access memory chips have noted that high density memory chips lack immunity of soft errors resulting from ionizing alpha particles. To overcome this problem, some manufacturers have improved the structures of the chips so as to provide a high degree of immunity to soft errors. While this approach reduces the likeliness of such soft errors, such errors still can occur which can give rise to uncorrectable error conditions.
Other manufacturers have proposed certain systems design alternatives. These include error correction, rewriting the corrected word to prevent error accumulation, periodic memory purging and systems redundancy. The soft error problems and the design alternatives are set forth in the publication "Memory System Design Seminar" by Intel Corporation, Copyright 1979.
It will be appreciated that while the above alternatives have been suggested, there appears to be no memory systems which have the ability to protect against soft errors.
Accordingly, it is a primary object of the present invention to provide a memory system with the capability of protecting against soft errors.
It is a further object of the present invention to provide a soft error protection capability by adding a minimum of additional apparatus to the memory system.